The research is designed to clarify auditory adaptation phenomena, which at present are poorly understood because of a variety of simultaneously-occurring phenomena produced by adaptation. On the basis of pilot study data, it appears that lateralization is affected to a greater extent and more rapidly than may have been suspected, and that lateralization changes may, in fact, produce perceptual judgment changes that can be interpreted as reflecting loudness decrements. Using a procedure worked out in a pilot study which limits differential adaption effects (which in turn cloud interpretation of results), the research will compare the growth of adaptation-produced lateralization shifts and loudness balancing changes for low and high frequency signals. Lateralization shifts will be measured at the median plane and the unadapted-ear location. The data will permit determination of adaptation effects upon lateralizations based on interaural time differences as well as interaural intensity differences; and will also permit a direct comparison of lateralization shifts with dichotic loudness balance changes. The possibility that ear dominance is related to ear differences in adaptation will also be studied. The investigator's conclusion from the pilot study data, that central interaction changes produced by adaptation reflect lateralization shifts primarily, and reflect binaural loudness summation changes only minimally, if at all, can be tested.